I think, depending on the relationship this child has with their PD specialist teacher that this might be one point of start.

Also if your school has a youth counsellor that is another potential avenue to explore.

Also, looking at the different books that portray different abilities - for example Ade Adepitan (Paralympian and TV presenter)  and perhaps write him a letter like a pen pall might help.

Hope this helps

Also as a general comment, I think psychological support for children who are coming to terms with a life long disability should be a fundamental part of the team around a child, alongside the usual practitioners like for example physio, ot, SLT. In our experience, in neurodisability, this does not happen as a matter of course.

Hello. I'm a parent of a daughter with cerebral palsy in mainstream who is now 14 (year 10, doing gcses). She is a powered wheelchair user who is hoisted for all transfers, has never walked, and relies on us, her parents, or carers for all her care needs. We have had to deal with similar questions also from a young age. I am happy to chat directly to you about what we have done and said over the years and also what external help we have got for her from camhs or school wellbeing. Best wishes

Involvement in a local/regional group for those with MD or a Whizz -Kidz Club help provide a yp with a  peer group that "gets it" , a place they feel they belong so would encourage Mum to explore what they have to offer.

Also sharing books where characters have impairments/ racial/cultural differences ,lots of lovely picture books ,some here but your local library service may also hold a list . https://www.scope.org.uk/advice-and-support/storybooks-featuring-disabled-children/#Disabled-children-in-the-picture-inclusive-storybooks